INTRODUCTION: One of the goals of conventional endodontic treatment is to minimize the amount of irritants that could be present inside the root canal system. OBJECTIVES: This study was designed to evaluate irrigant delivery using two different techniques in curved canals. MATERIALS AND METHODS: The mesiobuccal canals of 20 human extracted mandibular first molars were divided into two groups (n=10); Group (I) conventional syringe with side vented needle, Group (II) sonic irrigation (EndoActivator system). Contrast medium (OptirayTM 320, Mallinckrodt Inc. Hazelwood, MO, USA) was injected before, during and after canal preparation. All canals were prepared using Revo-S rotary system till reaching file AS35 using 5.25% NaOCl as an irrigant during instrumentation. Standardized preoperative, operative and postoperative digital radiographs were taken. The distance between full working length and the point of maximum irrigant penetration was measured using image editing software (DBS Win 5.3.1 and Image J). Data were then recorded and statistically analyzed. RESULTS: Sonic irrigation showed a statistical significant difference over the conventional needle and syringe group in increasing the depth of penetration of the contrast medium. CONCLUSIONS: the use of EndoActivator in irrigation had a superior effect in increasing the depth of penetration of irrigant when compared to conventional needle and syringe